Fiber-reinforced composites made with thermoplastic resin compositions and reactive coupling fibers

ABSTRACT

Methods of making fiber-resin compositions are described. The methods may include the providing of a thermoplastic resin to an extruder, where the thermoplastic resin may include at least one reactive moiety capable of forming a covalent bond with a coupling agent on a plurality of reactive fibers. The methods may further include combining the thermoplastic resin with the plurality of reactive fibers also supplied to the extruder. The reactive fibers are sized with the coupling agent that reacts with the thermoplastic resin to form the fiber-resin composition, which may be extruded from the extruder. Methods of making fiber-reinforced composite articles from the fiber-resin composition are also described.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a division of U.S. application Ser. No.15/639,065 filed Jun. 30, 2017, which is a continuation of U.S.application Ser. No. 15/285,563 filed Oct. 5, 2016, now U.S. Pat. No.9,725,564 issued Aug. 8, 2017, which is a division of U.S. applicationSer. No. 14/088,096, filed Nov. 22, 2013, now U.S. Pat. No. 9,493,612issued Nov. 15, 2016.

BACKGROUND OF THE INVENTION

Thermoset plastics are favored for making many kinds of fiber-reinforcedarticles because of their ease of manufacture. Uncured thermosets areoften low viscosity liquids at room temperature and easily wet a fabricof fibers. Once they have migrated through the fabric and surrounded itsfibers, a curing stage (sometimes called a hardening stage) commences topolymerize the thermoset into a polymer matrix. Often, this wetting andcuring takes place in a mold that defines the shape of thefiber-reinforced article.

The uncured thermoset resins used to make the composite are generallyinexpensive, but often off-gas irritating and sometimes dangerousvolatile organic compounds (VOCs). The outgassing of VOCs are ofparticular concern during curing, when the exothermic nature of manythermoset polymerization reactions raise the temperature of thecomposite and drive more VOCs into the gas phase. In many instances, itis necessary to cure large thermoset articles in facilities equippedwith robust ventilation and air scrubbing equipment, increasing theoverall production costs.

Thermoset articles are also difficult to repair or recycle. Hardenedthermoset resins often have a high degree of crosslinking, making themprone to fractures and breaks. Because thermosets normally will notsoften or melt under heat, they have to be replaced instead of repairedby welding. Compounding difficulties, the unrepairable thermoset partnormally cannot be recycled into new articles, but must instead belandfilled at significant cost and adverse impact on the environment.The problems are particularly acute when large thermoset parts, such asautomotive panels and wind turbine blades, need to be replaced.

Because of these and other difficulties, thermoplastic resin systems arebeing developed for fiber-reinforced articles that were once exclusivelymade using thermosets. Thermoplastics typically have higher fracturetoughness and chemical resistance than thermosets. They also soften andmelt at raised temperatures, allowing operators to heal cracks and weldtogether pieces instead of having to replace a damaged part. Perhapsmost significantly, discarded thermoplastic parts can be broken down andrecycled into new articles, reducing landfill costs and stress on theenvironment.

Unfortunately, thermoplastic composites have their own challenges. Theinterfacial strength between reinforcing fibers and resin matrix canplay a significant role in the performance of composite materials. Forthermoplastic resins such as polyamides, the challenge in promotingadhesion through conventional silane coupling agents is greater thanthat for thermosets, due to the low reactivity of many polymerizedthermoplastic resins. Thus, there is a need to develop new ways toimprove adhesion between reinforcing fibers and thermoplastic resins forimproved mechanical properties of the resulting composite materials.These and other issues are addressed in the present application.

BRIEF SUMMARY OF THE INVENTION

Methods of making and using extruded fiber-resin compositions in theconstruction of fiber-reinforced composite articles are described. Thepresent compositions include the combination of thermoplastic polymersand reactive fibers. The thermoplastic polymers may be melted andcombined with the reactive fibers in an extruder. The reactive fibershave been sized with one or more coupling agents that covalently bondthe thermoplastic resin to the fibers. An exemplary coupling reactionbetween the reactive fibers and the adjacent thermoplastic resin is thereaction between a deblocked isocyanate moiety on the coupling agent andan amide group on a polyamide resin. The covalent coupling between thefibers and thermoplastic resin provided by the coupling agent increasesthe tensile strength and other mechanical properties of fiber-reinforcedcomposite articles made with the present fiber-resin compositions.

Embodiments may include methods of making fiber-resin compositions. Themethods may include the providing of a thermoplastic resin to anextruder, where the thermoplastic resin may include at least onereactive moiety capable of forming a covalent bond with a coupling agenton a plurality of reactive fibers. The methods may further includecombining the thermoplastic resin with the plurality of reactive fibersalso supplied to the extruder. The reactive fibers are sized with thecoupling agent that reacts with the thermoplastic resin to form thefiber-resin composition, which may be extruded from the extruder.Methods of making fiber-reinforced composite articles from thefiber-resin composition are also described.

Embodiments may further include methods of making a fiber-reinforcedcomposite article. The methods may include providing a thermoplasticresin to an extruder, where the thermoplastic resin may include at leastone reactive moiety capable of forming a covalent bond with a couplingagent on a plurality of reactive fibers. The methods may further includecombining the thermoplastic resin with a plurality of the reactivefibers that are also supplied to the extruder. The plurality of reactivefibers are sized with the coupling agent. The methods may also includeextruding the fiber-resin composition from the extruder, where thethermoplastic resin reacts with the coupling agent on the reactivefibers to covalently bond the thermoplastic resin and the fibers in thefiber-resin composition. The fiber-resin composition may be formed intothe fiber-reinforced composite article.

Embodiments may yet further include methods of making a glassfiber-reinforced thermoplastic composite article. The methods mayinclude providing a thermoplastic resin to an extruder, where thethermoplastic resin may include at least one polyamide polymer. Thethermoplastic resin may be combined with a plurality of the reactiveglass fibers that are also supplied to the extruder, where the pluralityof reactive glass fibers are sized with a blocked isocyanate-containingcoupling agent covalently bonded to the glass fibers. The combination ofthe thermoplastic resin and the plurality of reactive fibers may beheated to deblock the isocyanate-containing coupling agent, which maythen react to form an acyl-urea bond with an amide moiety on thepolyamide polymer to form a fiber-resin composition. The fiber-resincomposition may be extruded from the extruder, and formed into the glassfiber-reinforced thermoplastic composite article.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the invention. The features and advantages ofthe invention may be realized and attained by means of theinstrumentalities, combinations, and methods described in thespecification.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings wherein like reference numerals are usedthroughout the several drawings to refer to similar components. In someinstances, a sublabel is associated with a reference numeral and followsa hyphen to denote one of multiple similar components. When reference ismade to a reference numeral without specification to an existingsublabel, it is intended to refer to all such multiple similarcomponents.

FIG. 1 is a flowchart showing selected steps in a method of makingfiber-resin compositions according to embodiments of the invention;

FIG. 2 is a flowchart showing selected steps in a method of making afiber-reinforced article according to embodiments of the invention;

FIG. 3 shows an exemplary system for making fiber-resin compounds andfiber-reinforced articles according to embodiments of the invention; and

FIG. 4 shows a exemplary fiber-reinforced article made according to thepresent methods.

DETAILED DESCRIPTION OF THE INVENTION

The present application includes methods of making exemplary fiber-resincompositions from thermoplastic resins and reactive fibers that includecovalently bonded coupling agents capable of bonding the fibers to thethermoplastic resins. By bonding the thermoplastic resin to the fibers,the strength of the fiber-reinforced article is significantly increased,and other mechanical properties may be improved. The fiber-resincompositions extruded from the extruder may be formed into afiber-reinforced composite article using a variety of thermoplasticmolding techniques. Details about the methods and systems used to makethe exemplary fiber-reinforced compositions and fiber-reinforcedcomposite articles are described below.

Exemplary Methods of Making Fiber-Resin Compositions

FIG. 1 is a flowchart showing an exemplary method 100 of making thefiber-resin compositions. The method 100 may include providingthermoplastic resin to an extruder 102. The thermoplastic resin mayinclude at least one reactive moiety capable of forming a covalent bondwith a coupling agent on a plurality of reactive fibers. The method 100may also include combining the thermoplastic resin with the plurality offibers that are also supplied to the extruder 104. Inside the extruder,the coupling agent on the plurality of fibers may be activated (e.g.,deblocked) to react with the reactive moiety on the thermoplastic resin106. A fiber-resin composition that includes the fibers bonded throughthe coupling agent to the thermoplastic resin may be extruded from theextruder 108.

The extruder configuration and extrusion technique may be selected basedon the size and type of fibers combined with the reactive resincomposition in the extruder. For example, when the plurality of fibersare chopped, short glass fibers (e.g., less than 0.5 inches in length) areactive extrusion technique may be used to produce the fiber-resincomposition. When the plurality of fibers are glass rovings, and/orcontinuous glass fibers, a direct-long fiber thermoplastic (D-LFT)extrusion technique may be used to produce the fiber-resin composition.Additional details about each of these extrusion techniques are providedas follows:

Exemplary Reactive Extrusion Techniques

Reactive extrusion is a low-cost, versatile extrusion technique thatinvolves the use of an extruder as a chemical reactor. Chemicalreactions associated with resins are carried out in situ while theextrusion process, including mixing of the resin composition with fibersand other reinforcement material, is in progress. Therefore, reactiveextrusion differs from conventional extrusion methods in which typicallyno chemical reactions occur during extrusion.

A reactive extrusion process may start by supplying short glass fibersand the reactive composition to the extruder. Once inside the extruder,the fibers and resin composition mix under conditions that promote thechemical reaction, such as formation of covalent bonding between thefibers and the resin.

When the short glass fibers have been sized with reactive compounds suchas coupling agents, the conditions in the extruder promote the reactionof the fibers with the thermoplastic resin. A coupling agent may formhighly reactive moieties in situ and covalently bond the thermoplasticresin to the fibers, improving the mechanical properties of thefiber-reinforced article made with the reactively extruded fiber-resincomposition.

Exemplary Long Fiber Thermoplastic Extrusion Techniques

Direct long fiber thermoplastic (D-LFT) molding is a technology wherethermoplastic resin is directly compounded with long glass fibers andthen molded in one operation. Different from a conventional extrusionprocess in which chopped fibers are used, in a D-LFT process continuousroving strands are fed into extruder. The advantage of D-LFT is theability to produce significantly longer glass fibers in the finalcomposite materials. In comparison to a standard LFT process based onlong fiber pellets, the D-LFT process doesn't produce semi-finishedmaterial. When D-LFT is used in compression or injection molding, amelted resin-fiber composition may transfer into a molding tool locatedin a compression press or directly injected into the molding.

Additional LFT processes may form pellets as a fiber-resin composition.The pellets have a typical length of ½ inch to up to 2 inches and areproduced by impregnating in a cross head tie. The reactive resincomposition may be combined with fibers typically at the end of anextruder and then further polymerized by applying heat prior to thechopping step. The pellets are semi-finished materials that can bemolded in a separate step, such as a compression step using aplasticator or in injection molding.

In both LFT and D-LFT processes the resulting composites contain longerglass fibers of ½″ (12 mm) up to 2″ (50 mm) in length. Longer fiberlength combined with excellent wet-out can provide improved mechanicalproperties such as higher stiffness and strength compared to shortfiber-reinforced composites made in a conventional extrusion processusing chopped fibers. Long-fiber reinforced thermoplastic compositesproduced in LFT and D-LFT processes are of great interest to manyindustries including automotive, due to their excellent mechanicalproperties and high stiffness-to-weight ratio.

Exemplary Fibers

The fibers may be one or more types of fibers chosen from glass fibers,ceramic fibers, carbon fibers, metal fibers, and organic polymer fibers,among other kinds of fibers. Exemplary glass fibers may include“E-glass’, “A-glass”, “C-glass”, “S-glass”, “ECR-glass” (corrosionresistant glass), “T-glass”, and fluorine and/or boron-free derivativesthereof. Exemplary ceramic fibers may include aluminum oxide, siliconcarbide, silicon nitride, silicon carbide, and basalt fibers, amongothers. Exemplary carbon fibers may include graphite, semi-crystallinecarbon, and carbon nano tubes, among other types of carbon fibers.Exemplary metal fibers may include aluminum, steel, and tungsten, amongother types of metal fibers. Exemplary organic polymer fibers mayinclude poly aramid fibers, polyester fibers, and polyamide fibers,among other types of organic polymer fibers.

The fiber length may range from short-to-intermediate chopped fibers(e.g., about 0.5 inches or less in length) to long fibers (e.g., morethan about 0.5 inches in length), including unchopped fibers, continuousfibers, rovings, and wound fibers, among others.

Reactive glass fibers may be formed by contacting glass fibers with asizing composition that includes a blocked isocyanate coupling compound.These coupling compounds include a moiety that covalently bonds thecompound to a surface on the glass fiber (e.g., a silicon-containingmoiety), and also include a blocked isocyanate group. The blockedisocyanate group may be represented by the formula:

where the “BLK” moiety represents a blocking group that can bereversibly bonded to the carbon atom of the isocyanate group.

Exemplary silicon-containing coupling moieties may be represented by:

Where R₁, R₂, and R₃ may be the same or different, and each mayrepresent an alkyl, aryl, alkoxy, halogen, hydroxyl, or cyclicstructure. Exemplary silicon-containing coupling moieties may includetrialkoxysilane groups such as —Si(OMe)₃, —Si(OEt)₃, etc.

Exemplary blocked isocyanate moieties may include an isocyanate group(—N═C═O) where the carbon is reversibly bonded to a blocking group. Theblocked isocyanate group may be obtained by reacting the free isocyanategroup with a compound that renders it unreactive. A suitable blockingagent for the isocyanate group may be determined by its ability toprevent the blocked isocyanate from reacting until a desired temperatureis achieved. Examples of compounds that may be suitable blocking agentsinclude, but are not limited to, oximes such as methyl ethyl ketoxime,acetone oxime, and cyclohexanone oxime, lactams such as ε-caprolactam,and pyrazoles. Organosilicon compounds with a blocked isocyanate groupare known in the art, e.g. see U.S. Patent Publication 2007/0123644,incorporated herein by reference. Upon heating or other deblockingconditions, these blocked isocyanates decompose to free isocyanate andthe blocking species. Deblocking temperatures depend on the blockinggroups and typically are in the range 70° C. to 200° C. When the sizedglass fibers with are exposed to unblocking conditions (e.g., elevatedtemperatures) the isocyanate group may become deblocked to form theactive isocyanate compound chemically bonded to the glass surface. Nowdeblocked, the isocyanate group is available to react with the adjacentthermoplastic polymer, coupling the polymer and glass fiber through thecoupling compound.

Exemplary coupling compounds may include blocked isocyanate couplingcompounds having a silicon-containing moiety and a blocked isocyanatemoiety. These blocked isocyanate coupling compounds may includecarboxamide compounds, carbamate compounds, and isocyanurate compounds,among others. Specific examples of carboxamide compounds include2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide. Specificexamples of carbamate compounds include triethoxysilylpropylethylcarbamate and (3-triethoxysilylpropyl)-t-butyl carbamate. Specificexamples of isocyanurate compounds include tris(3-trimethoxysilylpropyl)isocyanurate. Additional details about these and other exemplarycompounds, as well as methods of making them, can be found inco-assigned U.S. Pat. No. 8,293,322, entitled “SURFACES CONTAININGCOUPLING ACTIVATOR COMPOUNDS AND REINFORCED RESINS PRODUCED THEREFROM”,the entire contents of which are herein incorporated by reference forall purposes.

Exemplary sizing compositions may also include compounds that canenhance the fibers' physical characteristics in a number of waysincluding increased hardness, increased mechanical strength, greaterwettability, and increased adhesion between the fibers and resin. Forexample, the sizing compositions may include one or more of wettingagents, film-forming polymers, lubricants, defoamers, and biocides,among other compounds.

The reactive fibers may be formed by applying an exemplary sizingcomposition to the fibers by suitable methods known to one of skill inthe art. For example, the sizing composition may be applied to glassfibers pulled from a bushing using a kiss-roll applicator. Other ways ofapplying the sizing composition may include contacting glass fibers withother static or dynamic applicators, such as a belt applicator,spraying, dipping, or any other means.

Exemplary Thermoplastic Resins

The thermoplastic resin may include one or more polymers that can formcovalent bonds with the deblocked isocyanate moiety on the sized glassfibers of the substrate. For example, polyamide polymers (i.e., nylonpolymers) have an amide moiety capable of forming a covalent bond withthe deblocked isocyanate moiety. Specific examples of these polyamidepolymers may include polyamide-6; polyamide-6,6; polyamide-6,12;polyamide-4,6; polyamide-6,10; polyamide 12, polyamide 6T(polyhexamethylene terephthalamide); and polyamide 6I (polyhexamethyleneisophthalamide), among other polyamide polymers. The thermoplasticpolymer may also include combinations of two or more different polymers,such as two or more different polyamide polymers. In addition to thepolyamide polymers, exemplary thermoplastic polymers may includepolybutylene terephthalate (PBT) polymers, thermoplastic polyurethanes(TPUs), poly(styrene-co-maleic anhydride), maleated polypropylene,poly(hydroxyl-ethyl methacrylate), among other kinds of thermoplasticpolymers.

Exemplary Methods of Making Fiber-Reinforced Composite Articles

FIG. 2 is a flowchart showing an exemplary method 200 of making thefiber-reinforced composite articles. The method 200 may includeproviding a thermoplastic resin to an extruder 202. The thermoplasticresin may include at least one reactive moiety capable of forming acovalent bond with a coupling agent on a plurality of reactive fibers.The method 200 may also include combining the thermoplastic resin withthe plurality of fibers that are also supplied to the extruder 204.Inside the extruder, the coupling agent on the plurality of fibers maybe activated (e.g., deblocked) to react with the reactive moiety on thethermoplastic resin 206. A fiber-resin composition that includes thefibers bonded through the coupling agent to the thermoplastic resin maybe extruded from the extruder 208. The fiber-resin composition may thenbe formed into the fiber-reinforced composite article 210 byincorporating them into the article.

Exemplary techniques for forming the fiber-resin composition into thefiber-reinforced composite articles may include injection molding and/orcompression molding of the composition into the fiber-reinforcedarticle. Heat may be used in the compression molding of afully-polymerized fiber-resin composition to maintain the flowability ofthe composition as it is filling a mold or otherwise forming a shape ofthe final article.

Exemplary Composition and Article Fabrication Systems

FIG. 3 shows an exemplary system 300 for making the present fiber-resincompounds and fiber-reinforced articles. The system 300 includes asupply of a thermoplastic resin composition 302, and a supply of fibers304 that can be fed to an extruder 306. As noted above, systems 300 maybe configured to accept short fibers (e.g., short-chopped glass fibers),or long fibers. When the system 300 is configured to accept shortfibers, the extruder 306 is configured to conduct a reactive extrusionprocess to form the fiber-resin composition. Alternatively when thesystem 300 is configured to accept long fibers, extruder three or sixconfigured to conduct a D-LFT process to form the fiber-resincomposition.

The fiber-resin composition extruded by the extruder 306 may be directlysupplied to a molding machine 308 that forms the composition into thefiber-reinforced composite article. Exemplary molding machines 308 mayinclude injection molding machines, and compression molding machines,among other types of molding machines. A heated conduit (not shown) maybe used to maintain the fiber-resin composition in a molten/liquid stateas it is transported from the extruder 306 to the molding machine 308.Alternatively, the fiber-resin composition may be cooling or cooled asit moves from the extruder 306 to the molding machine 308.

Exemplary Fiber-Reinforced Composite Articles

FIG. 4 shows an exemplary fiber-reinforced composite wind turbine blade402 formed by the fiber-resin compositions. The blade 402 is one of manytypes of articles that can be formed by the present compositions. Otherarticles may include vehicle parts (e.g., aircraft parts, automotiveparts, etc.), appliance parts, containers, etc.

Having described several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theinvention. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent invention. Accordingly, the above description should not betaken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the fiber” includesreference to one or more fibers and equivalents thereof known to thoseskilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

What is claimed is:
 1. A fiber-resin composition for making afiber-reinforced article, the fiber-resin composition comprising: glassfibers comprising a coupling agent bonded to the glass fibers; and athermoplastic resin selected from the group consisting of polybutyleneterephthalate polymers, thermoplastic polyurethane polymers,polystyrene-co-maleic anhydride polymers, maleated polypropylenepolymers, and polyhydroxy-ethyl methacrylate polymers, wherein thecoupling agent comprises: (i) a silicon-containing moiety covalentlybonded to the glass fibers, (ii) a reactive isocyanate moiety capable offorming the covalent bond with at least one reactive moiety of thethermoplastic resin when a blocking group is released from the reactiveisocyanate moiety, and (iii) a linking moiety selected from the groupconsisting of an alkyl linker, and aryl linker, and an alkyl-aryllinker, wherein the linking moiety covalently bonds thesilicon-containing moiety and the reactive isocyanate moiety together inthe coupling agent.
 2. The fiber-resin composition of claim 1, whereinthe glass fibers have a length of less than 0.5 inches.
 3. Thefiber-resin composition of claim 1, wherein the glass fibers have alength ranging from 0.5 inches to 2 inches.
 4. The fiber-resincomposition of claim 1, wherein the glass fibers comprise at least onetype of glass selected from the group consisting of E-glass, A-glass,C-glass, S-glass, ECR-glass, and T-glass.
 5. The fiber-resin compositionof claim 1, wherein the fiber resin composition further comprises one ormore type of fibers selected from the group consisting of ceramicfibers, carbon fibers, metal fibers, and organic polymer fibers.
 6. Thefiber-resin composition of claim 1, wherein the silicon-containingmoiety has a formula of:

wherein R₁, R₂, and R₃ may be the same or different, and each mayrepresent an alkyl group, an aryl group, an alkoxy group, a halogen, ahydroxyl group, or a cyclic structure.
 7. The fiber-resin composition ofclaim 1, wherein the reactive isocyanate moiety has a formula of:

wherein BLK represents the blocking group that is reversibly bonded to acarbon atom on the reactive isocyanate moiety.
 8. The fiber-resincomposition of claim 7, wherein the blocking group is selected from thegroup consisting of oximes, lactams, and organosilicon compounds.
 9. Thefiber-resin composition of claim 8, wherein the oximes are selected fromthe group consisting of methyl ethyl ketoxime, acetone oxime, andcyclohexanone oxime.
 10. The fiber-resin composition of claim 8, whereinthe lactams comprise ε-caprolactam.
 11. A fiber-reinforced articlecomprising: glass fibers; and thermoplastic polymers selected from thegroup consisting of polybutylene terephthalate polymers, thermoplasticpolyurethane polymers, polystyrene-co-maleic anhydride polymers,maleated polypropylene polymers, and polyhydroxy-ethyl methacrylatepolymers, wherein the thermoplastic polymers are bonded to the glassfibers by a coupling agent that is covalently bonded to both the glassfibers and the thermoplastic polymers, wherein the coupling agentcomprises: (i) a silicon-containing moiety covalently bonded to theglass fibers, (ii) a reactive isocyanate moiety capable of forming thecovalent bond with at least one reactive moiety of the thermoplasticpolymers when a blocking group is released from the reactive isocyanatemoiety, and (iii) a linking moiety selected from the group consisting ofan alkyl linker, and aryl linker, and an alkyl-aryl linker, wherein thelinking moiety covalently bonds the silicon-containing moiety and thereactive isocyanate moiety together in the coupling agent.
 12. Thefiber-reinforced article of claim 11, wherein the glass fibers have alength of less than 0.5 inches.
 13. The fiber-reinforced article ofclaim 11, wherein the glass fibers have a length ranging from 0.5 inchesto 2 inches.
 14. The fiber-reinforced article of claim 11, wherein thearticle is selected from the group consisting of a turbine blade, avehicle part, an appliance part, and a container.
 15. A system formaking a fiber-reinforced article, the system comprising: a moltenpolymer amalgam comprising: glass fibers; and thermoplastic polymersselected from the group consisting of polybutylene terephthalatepolymers, thermoplastic polyurethane polymers, polystyrene-co-maleicanhydride polymers, maleated polypropylene polymers, andpolyhydroxy-ethyl methacrylate polymers, wherein the thermoplasticpolymers are bonded to the glass fibers by a coupling agent that iscovalently bonded to both the glass fibers and the thermoplasticpolymers, wherein the coupling agent used to bond the glass fibers andthe thermoplastic polymers originally comprised: (i) asilicon-containing moiety covalently bonded to the glass fibers, (ii) areactive isocyanate moiety capable of forming the covalent bond with atleast one reactive moiety of the thermoplastic polymers when a blockinggroup is released from the reactive isocyanate moiety, and (iii) alinking moiety selected from the group consisting of an alkyl linker,and aryl linker, and an alkyl-aryl linker, wherein the linking moietycovalently bonds the silicon-containing moiety and the reactiveisocyanate moiety together in the coupling agent; and a molding machinethat accepts the molten amalgam and molds it into the fiber-reinforcedarticle.
 16. The system of claim 15, wherein the supply of fibers areshort glass fibers having a length of less than 0.5 inches.
 17. Thesystem of claim 15, wherein the supply of fibers are long glass fibershaving a length ranging from 0.5 inches to 2 inches.
 18. The system ofclaim 15, wherein the blocking group is selected from the groupconsisting of oximes, lactams, and organosilicon compounds.
 19. Thesystem of claim 15, wherein the blocking group comprises ε-caprolactam.20. The system of claim 15, wherein the molding machine is selected fromthe group consisting of an injection molding machine and a compressionmolding machine.